1. Field of the Invention
Aspects of the invention relate generally to power conversion applications. More particularly, aspects are directed to optimization of multi-phase voltage converter efficiency regardless of load conditions.
2. Description of Related Art
Power conversion equipment is used to provide regulated power and a specified load current to a wide variety of devices, including microprocessors used in computers. Some equipment such as multi-phase buck voltage converters are designed to provide larger output current handling capabilities than single phase devices. For instance, a single phase converter providing a 100 A output current requires a MOSFET pair switch that is capable of supporting the full 100 A current.
Due to limitations in current ratings of such components, multiple phases are designed to carry the full load current. Thus, if five phases were employed to handle 100 A, the total current per phase is reduced by a factor of five. Some applications provide solutions having a fixed number of phases and a fixed gate drive voltage regardless of load variations.
By increasing the number of phases, the load current is divided by the number of phases. However, the power to drive the MOSFETs for the multiple phases increases. MOSFET driver power (Pdriver) is directly proportional to the combined MOSFET gate charge (QG), switching frequency (FSW) and driver voltage (VDRIVER) according to the following equation:Pdriver=QG×FSW×VDRIVER  (1)
Power for the MOSFET driver is constant for a given MOSFET combination (which determines the MOSFET total gate charge QG), switching frequency and drive voltage. If the same MOSFETs are used in all phases, the MOSFET driver power number is multiplied by the total number of phases. Conduction losses are proportional to the square of the load current (ILOAD—CURRENT) MOSFET “on” resistance (RDS-ON) and duty cycle, which is the ratio of output voltage to input voltage in a buck regulator. Total power conduction losses for both MOSFETs may be calculated according to the following equation:PCONDUCTION—LOSS=I2LOAD—CURRENT×RDS-ON  (2)
Systems and methods which reduce such conduction losses and adapt the driver voltage in multi-phase voltage converter applications are provided herein.